The present invention relates to an auxiliary drive arrangement of an internal combustion engine for an air compressor embodied as a single or multi-cylinder/piston compressor, with the piston or pistons that are guided in the cylinder or cylinders being driven, via a respective connecting rod, by a crankshaft that is connected to a drive gear or pinion that in turn is driven from the drive shaft of the internal combustion engine via gear wheels, whereby the air compressor pinion meshes with a gear wheel on a camshaft of the engine.
In contrast to air compressors having a V-belt drive, air compressors of the aforementioned general type that are driven by gear wheels have the tremendous advantage of having a maintenance-free drive mechanism. However, they also have the drawback that the compressed air that remains in the clearance or dead space of the air compressor after the top dead center position has been reached expands, as a result of which the tangential force that drives the air compressor suddenly becomes negative, and the air compressor looses torque. This leads to abrupt flank or side shifting or transition in the tooth mesh, along with an uncomfortable knocking noise. Aggravating the situation is that the greatest relative noise generation from the air compressor gear drive exists just when after a braking procedure, the engine is idling and the air tank is again filled with compressed air (for the compressed air units, such as the brakes, sliding doors or windows, etc.). Due to the low ignition pressures that exist in this situation, the idling noise of the engine is very low, and as a consequence the flank transition of the pair of gear wheels can be heard very distinctly.
A number of measures have become known for eliminating this drawback (i.e. reduction of the engagement side play), including:
1. conversion of the material pairing of the pair of gear wheels from steel to cast iron; PA0 2. use of a split air compressor play-compensating gear wheel; PA0 3. limiting the engagement side play by increasing the tooth gauge; PA0 4. adjustment of the play by an eccentric shifting.
All of these measures are either expensive to produce or are structurally complicated and require an additional expenditure on the engine assembly line or during air compressor exchange in the work shop. Furthermore, a number of possibilities for errors and imprecision result due to individual adjustment practices. The greatest drawback in conjunction with plays or clearances that are too narrow is, however, the increased axial pressure or load that acts over the entire periphery upon the air compressor mounting and crankshaft, as well as on the camshaft and camshaft mounting. With drive shafts that are mounted on roller bearings, peripheral loads represent greatly impeded operating conditions. Where the drive shafts are mounted on friction bearings, the constantly effective axial pressure results in a high bearing pressure and premature failure of the bearing. This ultimately leads to a reduced service life of the overall air compressor arrangement.
It is an object of the present invention to prevent the generation of noise at the tooth flanks or sides, especially in the region of the top dead center position of the piston or pistons of the air compressor, whereby however increased peripheral bending loads on the air compressor crankshaft and on the camshaft are to be avoided.